Kimrobinsonite is a very rare tantalum hydroxide mineral typically found as small, cubic crystals within highly evolved granitic pegmatites. It is primarily identified through chemical analysis due to its scarcity and similarity to other members of the pyrochlore supergroup.

Hardness

2.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Kimrobinsonite

Hardness: 2.5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this kimrobinsonite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch kimrobinsonite with a known reference. Kimrobinsonite sits at Mohs 2.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Kimrobinsonite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Kimrobinsonite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: colorless, white.
5
Look at form & habit
Crystal system: cubic. Typical habit: equant crystals.

Often found alongside kimrobinsonite

Minerals reported to co-occur with kimrobinsonite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Ta(OH)₅
Mohs hardness: 2.5
Density: 4.2 g/cm³
Colors: Colorless White
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Cubic
Crystal habit: Equant Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Granite Pegmatites
Typical price: $200-1000+ per specimen

Where rockhounds find kimrobinsonite

Classic worldwide localities

Kola Peninsula, Russia

Field-hunting tip

Look in granite pegmatites country — that is the host setting where kimrobinsonite typically forms. If you start seeing kesterite, stannite, quartz in float, you are in the right ground. Field specimens usually show a equant crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify kimrobinsonite?+

Mohs hardness is 2.5. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white.

Where is kimrobinsonite found?+

Notable localities include Kola Peninsula, Russia.

How much is kimrobinsonite worth?+

Typical asking prices fall in the range of $200-1000+ per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What minerals are found with kimrobinsonite?+

Kimrobinsonite commonly co-occurs with Kesterite, Stannite, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does kimrobinsonite form in?+

Kimrobinsonite typically forms in granite pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is kimrobinsonite used for?+

Kimrobinsonite is used in collector.

Find kimrobinsonite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.